ANTHOZOA. 57 



liave never exhibited any capability of locomotion. Some 

 species, when distiu'becl, become highly limiinous, inso- 

 much, that the statement of Linnfeus, that the "phos- 

 phorescent Sea-pens cover the bottom of the sea, and 

 there cast so strong a light that it is easy to count the 

 fishes and worms sj)orting among them," is by no means 

 devoid of foundation. 



Hitherto we have seen the solid part either stony 

 or ho]*ny, called the skeleton ov ])ohjinclom, deposited 

 witliin the living flesh, but there are some species of 

 Anthozoa in which it forms a protecting sheath to 

 the bodies of the Polypes which are lodged in its 

 interior. The elegant aggregation of tubes called 



The Organ-pipe Coral ^ Tuhipora*- Musica) is an example of such " 

 a structure (Fig, 39). It consists of small cyliudiical tubes of a 

 rich crimson hue, placed nearly i^arallel, but at a short distance 

 apart, and united at regular distances by successive stages of hori- 

 zontal plates, that divide the scries into ranges, or stories, like the 



FtG. 39.— OUGAN-l'IPE CORAL. 



different floors of a house supported by many pillars. From the 

 mouth of each tube, in the living state, protrude tiie eight tentacles 

 of a starry Polype of a brilliant green colour, forming a striking 

 contrast with the crimson polj^pidom. 



Actiniae.t — In the succeeding group of Polyj)es, while 

 the general form and structure of the Anthozoa are pre- 

 served, we find an organization much more complex than 



* Tubus, a tube ; porus, a pore. 

 t aKTlv, aktin, a ray. 



D 3 



